LT40 drive issues

cougarman42 · August 15, 2015, 09:29:58 PM

Hi all,
I've just joined this forum as I have a forward drive issue on my 06 LT40 hyd that I've had from new. I've checked all the obvious mechanical things ie. jams, tight rollers etc and taken the drive motor off so there is no load at all. I've learnt through this forum alot of guys seem to have had the same issue, no forward drive but it will reverse, and everything else works fine. It was good a few weeks ago and has only sat for maybe 4-5 weeks, previously its been all winter and no probs in the spring. Its normal these things happen on a weekend when WM are closed but I was hoping someone could advise?? Thanks.

Magicman · August 15, 2015, 09:42:11 PM

Welcome to the Forestry Forum, cougarman42. Yup, it seems that things happen on weekends. My first call would be to WM Monday AM for support and whatever parts are needed.

cougarman42 · August 15, 2015, 09:46:35 PM

Yeah that was my plan, it seems to be a common issue with circuit boards eh?

Magicman · August 15, 2015, 09:51:36 PM

The only time that I have had that problem it was a solenoid/relay and not a circuit board. The obvious thing to check are drum switch contacts.

Please add your location and sawmill to your profile which will help with future questions.

pineywoods · August 15, 2015, 10:48:56 PM

A call to wm is the logical action. Have a test light or voltmeter handy when you call. If you want to fiddle with it, here's a few things to try. Key switch on, drum switch in fwd, and speed control knob all the way down. Check for +12 volts on both terminals on the feed motor. If you don't the progression is back to the 2 big solenoids inside the left cover, thence to the fwd/rev drum switch, then to a couple of circuit breakers. You should feel the solenoids click when the fwd control is moved from neutral to fwd. On a 9 yr old mill, burned contacts on a solenoid or a broken or bent finger on the drum switch would be a high probability.
If you do have 12 volts on both terminals of the motor, then the likelyhood of electronic problems is high, although broken drum switch is possible.
In either case, you probably will need parts.
Post what the solution turns out to be, You may help someone else with a similar problem..

Brucer · August 16, 2015, 01:21:41 AM

First, an outline of how the feed system is wired. When the drum switch is set to the FWD position, it switches the speed control board into the motor feed. When the drum switch is in the REV position, the speed control board is bypassed completely. The speed control knob turns a potentiometer that adjusts the control board output.

The manual for your '06 mill has a section on troubleshooting the speed control circuit (it's in section 6.6 in my manual). This tells you how to isolate problems by looking at LED's on the circuit board.

Before you call WM, it would be a good idea to open up your control panel and find those LED's.

I always remove the negative battery lead before I open the front or back of the control panel. Once it's opened up I make sure there are no wires touching any metal. Then I reconnect the negative battery lead.

Chuck White · August 16, 2015, 06:29:07 AM

Quote from: Brucer on August 16, 2015, 01:21:41 AM
First, an outline of how the feed system is wired. When the drum switch is set to the FWD position, it switches the speed control board into the motor feed. When the drum switch is in the REV position, the speed control board is bypassed completely. The speed control knob turns a potentiometer that adjusts the control board output.

The manual for your '06 mill has a section on troubleshooting the speed control circuit (it's in section 6.6 in my manual). This tells you how to isolate problems by looking at LED's on the circuit board.

Before you call WM, it would be a good idea to open up your control panel and find those LED's.

I always remove the negative battery lead before I open the front or back of the control panel. Once it's opened up I make sure there are no wires touching any metal. Then I reconnect the negative battery lead.

Welcome to the Forestry Forum, cougarman42.

Another safety precaution that I do whenever I open the control panel, and the power will be on, is to take a length of small gasoline line that I have split the full length and slid that over the bottom lip of the opening on the control panel front access.

Doing this will prevent hot wires from contacting any metal! Don't ask me how I know! :-\

Ga Mtn Man · August 16, 2015, 07:56:31 AM

Quote from: pineywoods on August 15, 2015, 10:48:56 PM...If you don't the progression is back to the 2 big solenoids inside the left cove

FYI, my 2012 LT40 non-Super doesn't have these solenoids.

Sixacresand · August 16, 2015, 09:46:02 AM

Welcome to the Forum, Cougarman42
My LT40 experienced the same problem. After some tests, under the guidance a WM Tech on the phone, it was determined a electronic module that controlled the forward motion was defective. The next day I received a replacement part and was running again just a few minutes. The tech advised me that I should turn down the speed control knob before reversing the head.

cougarman42 · August 16, 2015, 01:28:00 PM

First of all thanks for all the replies, it helps to talk it over with experienced sawyers.
I checked the drum switch first and there is power in the right places, with the drum switch in forward there is 12v on both motor terminals. The LED's on the control module show power and OL which I assume is overload although with the motor unbolted and even the pulley removed there is no load. The motor brushes are fine on inspection so I'm thinking electronic sounds likely? I guess the pot for the speed control could be at fault too, anyone know how to test it?

deadfall · August 16, 2015, 01:32:42 PM

Quote from: cougarman42 on August 16, 2015, 01:28:00 PM
I guess the pot for the speed control could be at fault too, anyone know how to test it?

Out of the circuit with an ohmmeter. That's not from under my W-M sawyer hat, but my long ago navy Electronics Tech hat. I should let the W-M experts tell you.

cougarman42 · August 16, 2015, 02:12:38 PM

Ok I'll call tomorrow and I'll post the result after I get sorted out! Thanks to all again, happy milling.

pineywoods · August 16, 2015, 02:37:36 PM

OK, more checks. If you have +12 on both motor terminals, that says the speed control package is not pulling one terminal to ground to make the motor go. The speed control pot feeds that little black plastic module with the lights on it. One of the lights is labeled "in". with the key switch on, the in light should should go from dim to bright when you turn up the speed control. Likewise the light labeled "out". One final check. Find the blue wire coming out of the speed control module. There is a slip-on terminal on the end that connects to a push-on terminal on the main board. Pull it off. Use a jumper wire to momentarily connect +12 volts to the terminal on the main board. If the motor runs, the speed control module is bad, if not, it's the mosfet assembly which is actually the back cover on the control box. Most likely the speed control module bad. Take the back cover off to get to it. When installing a new one, change 1 wire at a time, they are color coded.

OH BTW, pull the negative cable off the battery before you go messing around in there....